Field of the Invention
The present invention pertains to apparatuses and methods for separation of constituents of a multi-constituent liquid solution or suspension.
Background Information
Developing methods and apparatus for separating organics (oil & greases, and biological materials) from raw water streams is important in many industries, including the oil & gas industry. The term “raw waters” is an industry term for describing waste-containing waters and is used hereafter to refer to any water that requires treatment, including but not limited to industrial, agricultural, domestic and potable water.
Whether simply considering environmental issues, or costs and effectiveness in complying with associated regulations and best practices, separating contaminants from raw waters is of increasing importance for 1) oil and gas industry flow-back water from hydraulic fracturing; 2) oil and gas industry produced water that flows from the wells during the production of oil and/or gas; 3) raw waters generated in the processing of food (e.g., meat and poultry); 4) sea water contaminated with oils and greases and biological materials; 5) municipal water supplies; and others.
Separating solids from liquids is nothing new—it has been practiced in various forms for hundreds of years. However, various new processes, devices and materials have been suggested during the past few decades in the never-ending quest for more effective and/or more efficient and cost-effective filtration methods and systems.
One widely accepted separation method involves Aluminum polymers, such as poly-aluminum hydroxychloride (also known as aluminum chlorohydrate or ACH), poly-aluminum chloride (PAC), or poly-aluminum siloxane sulfate (PASS). These polymers are often chemically combined with quaternized polymers, such as di-allyl di-methyl ammonium chloride (DADMAC), and are added to water to create flocculent materials that can be removed by skimming or filtration.
In recent years, membrane filtration has been shown to be one of the best methods for large-scale separation of raw water. Processing factors, such as recyclability of throughput material in cross flow membrane assemblies, ease of cleaning, as well as highly pure permeate with no chemical tainting are among the attractive features of this approach. A significant drawback of membrane purification, however, is membrane fouling. Fouling can arise from a number of factors, such as adsorption inside the membrane, deposition on the membrane surface to form a cake layer, and blocking of the membrane pores.
Membranes with hydrophilic surfaces have exhibited more desirable anti-fouling properties than more hydrophobic (less hydrophilic) membranes. It is envisioned that such properties are due to hydrophilic membranes being less sensitive to adsorption. However, industry has yet to achieve a suitably hydrophilic membrane that also meets other necessary or desirable performance characteristics. Prior approaches have concentrated on either fabricating membranes from hydrophilic polymers, or attaching high molecular weight hydrophilic materials to inorganic membranes.
This latter category of approaches includes surface segregation, surface coating, and surface graft polymerization. However, many of these methods have limitations that the present inventor now can show are avoidable. For instance, ceramic membranes offer good commercializable methods for separation. However, currently available ceramic membranes require very small pores (≤50 nm) for hydrocarbon/water separation. Such small pore sizes tend to decrease fluid flow rate and promote clogging. Furthermore, typical ceramic membranes are readily fouled by biological material from viruses, bacteria, and proteins. Attempts to overcome these small-pore issues results in other problems, including requirements for high flow rate pressures (involving higher equipment costs and energy consumption), or the need for less effective, much larger membrane pores. In any event, fouling still occurs through use of currently available ceramic membranes at rates now known by the present inventor to be avoidable through cost-effective and otherwise efficacious means. With fouling comes low net permeate rates, requirements for back-flushing of the permeate to clear the membrane, and often a shortened service life of the membrane (with associated elevated costs).
Therefore, while there is a compelling need to develop ever-more efficacious and cost-effective filtration systems and methods, and particularly ones that reduce or eliminate the present approaches' limitations of requiring multiple, time-consuming steps; high equipment costs; and significant energy consumption, it is clear that current industry investigative pathways including material science (e.g., substrate materials), manufacturing methods (e.g., sintering, casting, laser etching), and high molecular weight coatings teach away from the materials and methods of the present invention that (as described below) achieves just such objectives. In other words, industry experts and researchers have tried, but failed to achieve the hydrophilicity and organophobic performance of alumina-based reactant surfaces that are achieved through practice of the present invention, and, therefore, also failed to achieve long-needed filtration performance characteristics that are likewise first made possible by the present invention.
Practice of the present invention also reduces the number of steps, or time consumed by steps in effective filtration, is most cost effective per unit volume of processed raw waters, and/or reduces energy consumption associated with filtration will substantially benefit industry, as well as society at-large. Some benefits from such improved filtration may be apparent (direct operating costs savings, reduction in capital expenditures, reductions in labor costs, removing “choke points” in processes that involve filtration, and so on). However, other, less apparent benefits arise as well. For example, when filtration can be achieved cheaper, faster, with less labor requirements, and with simpler and/or smaller systems, many economic and practical barriers to the utilization of filtration systems and methods are substantially reduced. In many instances, this translates into higher levels of compliance with environmental regulations and associated reduction in overall environmental impact from many industrial processes.
As is described below, practice of the present invention affords the opportunity to meet, not just one, but all of the objectives of achieving optimal filtration of raw water by reducing direct operating costs, reducing capital expenditures for filtration systems, reducing labor costs, and removing “choke points” in processes that involve filtration (by accelerating the filtration process for a unit volume of raw water, when compared to conventional systems and methods).